#9 Regular Envelopes (3-7/8? x 8-7/8?) are one of the most popular commercial-sized envelopes available, commonly used as a reply envelope for invoice and business mailings, sent to recipients inside #10 Envelopes in order to mail something back to the sender. In this bright, saturated Electric Coral color, this envelope is sure to stand out. This #9 size envelope is constructed from 24lb. paper. Available both plain or custom printed for branding, address printing services are also available. These envelopes are sealed by a moistenable glue on the back flap.